Mapping and ablation catheters are well-established technologies that allow the physician to locate and treat damaged cardiac tissue. Presently, a considerable amount of time is often spent by the physician when manipulating such catheters within cardiac structures, such as the right atrium, simply trying to locate an anatomical feature of interest, such as the coronary sinus ostium.
A pre-shaped guiding catheter is typically used to blindly locate the coronary sinus ostium, but this endeavor is complicated by the fact that the location of the coronary sinus ostium may vary appreciably from one patient to another, especially among patients with diseased hearts. Oftentimes, the clinician is entirely unable to locate the coronary sinus ostium using the guiding catheter, and must resort to finding the ostium by “mapping” (interpreting localized bipolar waveforms) using an electrophysiological (EP) catheter and an ECG monitor. After the ostium is located, a guiding catheter or sheath is typically used to inject radiographic contrast media into the coronary sinus to highlight the associated venous system, and then a pacing lead is installed within one of the coronary branches.
Steerability is also important for ablation catheter implementations. In many cases, ablation of the damaged tissue can restore the correct operation of the heart. Ablation can be performed, for example, by percutaneous ablation, a procedure in which a catheter is percutaneously introduced into the patient and directed through an artery to the atrium or ventricle of the heart to perform single or multiple diagnostic, therapeutic, and/or surgical procedures. In such a case, an ablation procedure is used to destroy the tissue causing the arrhythmia in an attempt to remove the electrical signal irregularities or create a conductive tissue block to restore normal heartbeat or at least an improved heartbeat. Successful ablation of the conductive tissue at the arrhythmia initiation site usually terminates the arrhythmia or at least moderates the heart rhythm to acceptable levels. A widely accepted treatment for arrhythmia involves the application of radio frequency (RF) energy to the conductive tissue.
By way of example, a procedure to address atrial fibrillation, referred to as Cox's Maze procedure, involves the development of continuous atrial incisions to prevent atrial re-entry and to allow sinus impulses to activate the entire myocardium. While this procedure has been found to be successful, it involves an intensely invasive approach. It is more desirable to accomplish the same result as the Maze procedure by use of a less invasive approach, such as through the use of an appropriate electrophysiological (EP) catheter system having enhanced steering and shape adjustment capabilities.
Steerable conventional mapping and ablation catheter systems are typically configured to allow the profile of the distal end of the catheter to be manipulated from a location outside the patient's body. The contours of pre-shaped diagnostic catheters, for example, are generally fixed, and this is typically achieved in production by constraining the distal end within a shaping fixture while warming them until they assume the intended shape (i.e., by “heat setting” their polymer shaft). The shape of steerable mapping catheters, on the other hand, can be altered by the user simply by applying tension to one or more internal steering tendons affixed to a distal-end tip of the catheter. However, most steerable mapping catheters are generally straight when no tension is applied to the tendons. When steered, the distal end of such steerable catheters assumes a semicircular arc or full circular shape whose radius of curvature depends upon the amount of tension applied to the steering tendon.
FIGS. 1 and 2 illustrate a conventional steerable catheter in a relaxed configuration and a steered configuration, respectively. Catheter 20 is shown to include a number of band electrodes 22 and a tip electrode 24. As can be seen in FIG. 1, catheter 20 maintains a relatively straight profile while in a relaxed configuration.
FIG. 2 illustrates the catheter 20 of FIG. 1 in a steered configuration. According to this and other conventional steerable catheter implementations, catheter 20 has a distal end that assumes a semicircular arc or a fully circular shape when tension is applied to the catheter's steering tendon(s). The circular arc of catheter 20, when in its steered configuration, develops a shape whose radius, R, of curvature depends upon the amount of tension applied to the distal end vis-à-vis the steering tendon(s). It will be appreciated by those skilled in the art that enhanced steering capabilities are often required over and above those offered by conventional steerable catheters, such as those of the type depicted in FIGS. 1 and 2, for locating (e.g., such as by mapping) certain anatomical features and performing an ablation technique once such anatomical features have been located and accessed.
There is a need for an improved steerable catheter having enhanced steering capabilities for mapping and ablation applications. There exists a further need for such a catheter that provides for increased lumen space for accommodating larger payloads and one that resists deformation after repeated steering. The present invention fulfills these and other needs, and addresses other deficiencies of prior art implementations.